Method and system for power control of ionic cleaners for ice machines using pulse width modulation

ABSTRACT

A method for decontaminating air in an ice making machine, comprising: controlling the level of ozone outputted from an ozone generator by modulating the voltage using pulse width modulation; and contacting the air with the ozone.

CROSS-REFERENCED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/370,793, filed on Aug. 4, 2010, which is incorporated herein in its entirety.

BACKGROUND

1. Field

The present disclosure generally relates to a method and system for varying the output of an ionic cleaning device in an ice making machine based on machine volume by way of input voltage pulse width modulation.

2. Discussion of the Background Art

Commercial ice-making machines and beverage dispensing machines are susceptible to contamination by microorganisms such as bacteria, yeast, fungi, and mold. Once this equipment has become contaminated, these microorganisms may multiply and establish flourishing colonies that can form scale buildup in the lines, tubing, evaporator surfaces, drains and other parts of the machines. Furthermore, these microorganisms may present a serious health hazard to people ingesting the contaminated products dispensed from the ice or beverage machines.

The need to keep ice making and beverage dispensing equipment clean over time is well known. Therefore, in an ice-making machine, for example, the ice-forming evaporator, fluid lines and ice storage areas of the ice machine must be periodically cleaned. While manual cleaning with detergents and sterilizing chemicals may be effective, cleaning schedules are not, as a practical matter, always adhered to nor may the job always be satisfactorily completed in terms of a thorough cleaning and rinsing of all the contacted surfaces. Thus, systems have been developed that include electronic controls to automatically execute a sanitizing cycle at set periods wherein cleaning agents are pumped through the system and then rinsed out. Of course, the automatic systems can fail as well, where, for example, the cleaning agent reservoir runs out of cleaner, or the apparatus simply breaks down or fails to operate properly.

The use of ozone (O₃) as a sanitizing/oxidizing agent is well known, and especially well known is the use of O₃ to kill microorganisms in water. In U.S. Pat. No. 6,153,105, Tadlock et al. placed a venturi in the circulating water line of an ice machine to use the circulating water as a motive fluid to entrain ozone from a corona discharge process into the circulating water. The corona discharge process generates ozone at a pressure below the potable water supply pressure to the ice machine, thereby requiring the use of a venturi. Thus, the circulating water, with the venturi, carries O₃ over the ice making evaporator providing some bactericidal or bacteriostatic effect.

Ozone may also be produced by electrolysis, which advantageously can produce ozone at pressures greater than that of the circulating water line within the ice machine. Therefore, the ice machine would not require a venturi or other apparatus to inject the ozone into the water line. Electrolytic production of ozone occurs in an electrochemical cell by causing oxidation and reduction reactions that liberate or consume electrons. These reactions take place at electrode/solution interfaces, where the electrodes must be good electronic conductors. In operation, a cell is connected to an external load or to an external voltage source, and electrons transfer electric charge between the anode and the cathode through the external circuit. To complete the electric circuit through the cell, an additional mechanism must exist for internal charge transfer. One or more electrolytes provide internal charge transfer by ionic conduction. These same electrolytes must be poor electronic conductors to prevent internal short-circuiting of the cell.

Proton exchange membranes (PEM's) are one category of electrolytes that are particularly suitable for use in conjunction with the production of ozone in electrochemical cells. PEM's typically have a polymer matrix with functional groups attached that are capable of exchanging cations or anions. The polymer matrix generally consists of an organic polymer such as polystyrene, or other polytetrafluoroethylene (PTFE) analog. In general, the PEM material is an acid with a sulfonic acid group incorporated into the matrix.

Electrocatalysts are placed in intimate contact with the proton exchange membranes. Typical electrocatalysts for an ozone generator may be lead dioxide on the anode or ozone producing side of the cell and platinum black on the cathode side of the electrochemical cell. In many such cells, hydrogen gas is generated at the cathode as a byproduct of the electrolysis reaction that produces ozone at the anode.

Ultraviolet radiation can also been known to kill microorganisms in water and other liquids. Conventionally, the ultraviolet light source is a mercury-vapor type lamp, producing the majority of the radiated energy at a wavelength of about 254 nanometers, a wavelength know to be effective in killing microorganisms in water. The lamp may be immersed in the water or liquid or the lamp may be placed adjacent to a liquid stream flowing in a transparent conduit or in a conduit having a transparent window through which the ultraviolet radiation may pass. In U.S. Pat. No. 6,153,105, Tadlock et al. uses ultraviolet radiation to treat the circulating water in an ice machine.

While Tadlock et al. and others have made strides in treating water in ice machines and beverage machines, there are still problems that need to be solved. Because the water circulates throughout the system in the icemaker, microorganisms have the opportunity to grow and flourish because the water circulation gives the microorganisms the residence time required for them to multiply and establish colonies. Furthermore, additional microorganisms are introduced into the system whenever the makeup water fills the reservoir by batch. Accordingly, water treatment must occur when the batch is brought into the reservoir at a fairly high rate, making adequate treatment more difficult. Ozone treatment is made more difficult because the source of the ozone must be capable of varying the ozone production rate in proportion to the water refill rate up to an amount adequate to treat a large influx of water when the batch fill of the reservoir takes place.

What is needed is an apparatus that can treat ice making and beverage dispensing machines to keep them free of microorganism contamination. It would be an advantage if such an apparatus could provide disinfecting quantities of biocide on demand in response to a batch filling of the reservoir. It would be further advantageous if the apparatus could provide and distribute the biocide sufficiently to preclude microorganism growth throughout the system, including both the areas used to produce the ice or beverage and the areas used to dispense the ice or beverage.

U.S. Pat. No. 7,029,587, which is incorporated by reference in its entirety, provides an ice machine and a method for decontaminating air. An ice machine of the present invention comprises a makeup water conduit comprising one or more ultraviolet transmission surfaces and one or more ozone injection ports and a circulating water conduit comprising one or more ultraviolet transmission surfaces and one or more ozone injection ports. Typically, the water is circulated by a circulating pump from a water reservoir to evaporator plates. The ice machine further comprises one or more ultraviolet radiation sources that are adjacent to the ultraviolet transmission surfaces and an ozone generator in fluid communication with the one or more ozone injection ports. The ultraviolet radiation sources may be an ultraviolet lamp that produces a majority of its ultraviolet radiation at about 254 nanometers. Also, the ice machine comprises one or more controllers, wherein the controllers start and stop the one or more ultraviolet radiation sources, the ozone generator, or combinations thereof.

Typically, the ozone injection ports are located either upstream or downstream of each of the one or more ultraviolet radiation sources or combinations thereof. The ozone injection ports may be located less than one conduit diameter downstream of the one or more ultraviolet radiation sources or alternatively, less than three conduit diameters downstream of the one or more ultraviolet radiation sources.

The ozone generator typically comprises an electrolyzer. The ozone leaves the ozone generator as a gas, as ozonated water or as combinations thereof. When the ozone generator produces gaseous ozone, the generator may further comprise at least one hydroscopic membrane, wherein the gaseous ozone may pass through the membrane and water cannot pass through the membrane.

The ozone generator may be in fluid communication with each of the ozone injection ports. The one or more controllers for starting and stopping ozone generation communicate electrical signals, mechanical signals, or combinations thereof with devices such as a refrigeration compressor, a condenser fan, and/or the circulating pump.

The step of controlling ozone production may further comprise receiving a communication signal from the controller to push an anode electrode against a proton exchange membrane, wherein the communication from the controller may be an electrical signal, a mechanical signal or combinations thereof. The controller may be an electrical device, a mechanical device, or combinations thereof The controller may be a bourdon tube, a set of bellows, or a hydraulic piston. The motive fluid to move the controller may be a refrigerant from a compressor discharge line or pressurized water from the circulating pump discharge or a potable water supply. The ozone generator is typically in fluid communication with each of the one or more ozone injection ports.

The disadvantage of the conventional ozone generator cleaners used in ice making machines is that the typically contact ozone with water, which does not sufficiently prohibit bacteria growth in the ice making machine. Others have used ozone to treat the air, however, such conventional ozone generators which have been used to treat air in ice making machines are continuously powered with a DC voltage (i.e., 12 volts at 600 milliamps) to energize the ultraviolet (UV) light bulb, which in turn ionizes (by ozone or other ions) the air and helps with sanitation of the food zone in an ice machine. The amount of ionization depends on the amount of average power applied to the device.

The present inventors have unexpectedly discovered that by varying the output level of an ionic cleaning device excess ozone production can be avoided. That is, if the ozone level being introduced into an ice machine exceeds approximately 0.1 ppm exposure to operates, then there can be potential health associated issues. Thus, it would be desirable to maintain the ozone level to which the operator is exposed during operation to less than 0.1 ppm. The present disclosure provides for a method of controlling or manipulating the amount of ozone level output from an ionic cleaner disposed within an ice machine by use of pulse width modulation (PWM) of the DC voltage input to the device. That is, the present disclosure modulates the amount of ozone introduced into the ice machine by controlling or manipulating the grams per hour of ozone introduced from the ionic cleaner into the ice machine.

The present disclosure also provides many additional advantages, which shall become apparent as described below.

SUMMARY

A method for decontaminating air in an ice making machine, comprising: controlling the level of ozone outputted from an ozone generator by modulating the voltage using pulse width modulation; and contacting the air with the ozone. Preferably, the level of ozone is about less than 0.1 ppm.

The pulse width modulation controls the level of the ozone by controlling or manipulating the grams per hour of ozone introduced from the ozone generator into the ice making machine.

The method further comprises: comparing the model of the ice making machine to a look-up table; and determining the percentage of the pulse width modulation require to control the voltage by calculating the ‘on’ time and frequency for a pulse width modulation driver transistor based upon the model.

The modulated voltage produced from the pulse width modulation is generated by an ozone control signal from a processor module and a pulse width modulation circuit. The pulse width modulation circuit comprises at least one driving resistor and a field effect transistor. Preferably, the field effect transistor is a metal oxide semiconductor field effect transistor.

An ice making machine comprising: an condenser; a compressor; an evaporator disposed within an ice making zone; and an ozone generator in communication with the ice making zone, wherein the level of ozone outputted from the ozone generator is controlled by modulating the voltage using pulse width modulation; and contacting air withdrawn from the ice making zone with the ozone and returning it to the ice making zone.

Further objects, features and advantages of the present disclosure will be understood by reference to the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an ionic cleaner power control used according to the present disclosure;

FIG. 2 is a logic diagram pertaining to the control of the power used to produce ozone in an ionic cleaner by PWM;

FIG. 3 depicts a PWM driver circuit according to the present disclosure;

FIG. 4 is an oscilloscope capture demonstrating that both the current and voltage vary as the PWM % varies;

FIG. 5 is a block diagram of a microprocessor according to the present disclosure; and

FIG. 6 is a partial left side rear review of the ozone generator or ionic cleaner disposed within an ice making machine according to the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present disclosure includes the installation of an ionic cleaner device inside an ice making machine to release an ion/ozone discharge into the food zone of the ice making machine to aid in prolonged sanitation of the machine. The ionic cleaner device preferably uses a DC voltage power input. In order to manipulate the ion/ozone output of the ionic cleaner device and, thus, the ion/ozone concentration that build up inside the ice making machine, the present disclosure provides for the use of pulse width modulation to control how much output the ionic cleaner device has based on what the internal volume is for the ice making machine and bin assembly.

Pulse width modulation (PWM) is a very efficient way of providing intermediate amounts of electrical power between fully on and fully off. A simple power switch with a typical power source provides full power only when switched on. PWM is a comparatively recent technique and not previously known to have been used for the dispensing of ozone as recited in the present disclosure.

Basically, a PWM variable-power scheme is capable of switching the power quickly between fully on and fully off. In any event, the switching rate is much faster than what would affect the load, which is to say the device that uses the power. In practice, applying full power for part of the time does not cause any problems.

The term duty cycle describes the proportion of on time to the regular interval or period of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on. PWM works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.

PWM of a signal or power source involves the modulation of its duty cycle, to either convey information over a communications channel or control the amount of power sent to a load.

Digital circuits generate PWM signals (e.g., many microcontrollers have PWM outputs) and they normally use a counter that increments periodically (it is connected directly or indirectly to the clock of the circuit) and which is reset at the end of every period of the PWM. When the counter value is more than the reference value, the PWM output changes state from high to low (or low to high). This technique is referred to as time proportioning, particularly as time-proportioning control—which proportion of a fixed cycle time is spent in the high state. The incremented and periodically reset counter is the discrete version of the intersecting method's sawtooth. The analog comparator of the intersecting method becomes a simple integer comparison between the current counter value and the digital (possibly digitized) reference value. The duty cycle can only be varied in discrete steps, as a function of the counter resolution. However, a high-resolution counter can provide quite satisfactory performance.

Four types of pulse-width modulation (PWM) are possible:

1. The pulse center may be fixed in the center of the time window and both edges of the pulse moved to compress or expand the width.

2. The lead edge can be held at the lead edge of the window and the tail edge modulated.

3. The tail edge can be fixed and the lead edge modulated.

4. The pulse repetition frequency can be varied by the signal, and the pulse width can be constant. However, this method has a more-restricted range of average output than the other three.

PWM can be used to reduce the total amount of power delivered to a load without losses normally incurred when a power source is limited by resistive means. This is because the average power delivered is proportional to the modulation duty cycle. With a sufficiently high modulation rate, passive electronic filters can be used to smooth the pulse train and recover an average analog waveform.

High frequency PWM power control systems are easily realizable with semiconductor switches. The discrete on/off states of the modulation are used to control the state of the switch(es) which correspondingly control the voltage across or current through the load. The major advantage of this system is the switches are either off and not conducting any current, or on and have (ideally) no voltage drop across them. The product of the current and the voltage at any given time defines the power dissipated by the switch, thus (ideally) no power is dissipated by the switch. Realistically, semiconductor switches such as MOSFETs or bipolar junction transistors (BJTs) are non-ideal switches, but high efficiency controllers can still be built.

During the transitions between on and off states, considerable power is dissipated in the switches. However, the change of state between fully on and fully off is quite rapid relative to typical on or off times, and so the average power dissipation is quite low compared to the power being delivered.

The present disclosure utilizes PWM as an efficient voltage regulators in the generation of ozone from an ionic generator cleaner. By switching voltage to the load with the appropriate duty cycle, the output will approximate a voltage at the desired level. The switching noise is usually filtered with an inductor and a capacitor. One method measures the output voltage. When it is lower than the desired voltage, it turns on the switch. When the output voltage is above the desired voltage, it turns off the switch.

The present disclosure varies the average power by varying the average voltage applied to the ionic cleaner device, by performing a pulse width modulation on the voltage waveform. Preferably, the controller software automatically decides the amount of the PWM based on the type of ice making machine, e.g., the size or capacity of the ice making machine. That is, the smaller the ice making machine's capacity, the lower its average power and, thus, the lower the PWM setting. Alternatively, the PWM setting can be selected manually via a user interface as a menu item on the controller display.

The present disclosure can best be understood by reference to the attached drawings, wherein FIGS. 1 and 5 depict the different elements/components that are involved in controlling the ionic cleaner used with an ice making machine. That is, the processor module 115 preferably encompasses a microcontroller 105, firmware or a program 125 that has the logic to generate a control signal and also to recognize the model of the ice making machine based on data entered into the controller 105 via a user interface 110 and comparing it with the model stored in the non-volatile memory 120.

Controller 105 includes a user interface 110, a processor 115, and a memory 120. Controller 105 may be implemented on a general-purpose microcomputer. Although controller 105 is represented herein as a standalone device, it is not limited to such, but instead can be coupled to other devices (not shown) via network 130, if deemed necessary.

Processor 115 is configured of logic circuitry that responds to and executes instructions.

Memory 120 stores data and instructions for controlling the operation of processor 115. Memory 120 may be implemented in a random access memory (RAM), a hard drive, a read only memory (ROM), or a combination thereof One of the components of memory 120 is a program module 125.

Program module 125 contains instructions for controlling processor 115 to execute the methods described herein. For example, as a result of execution of program module 125 and processor 115. The term “module” is used herein to denote a functional operation that may be embodied either as a stand-alone component or as an integrated configuration of a plurality of sub-ordinate components. Thus, program module 125 may be implemented as a single module or as a plurality of modules that operate in cooperation with one another. Moreover, although program module 125 is described herein as being installed in memory 120, and therefore being implemented in software, it could be implemented in any of hardware (e.g., electronic circuitry), firmware, software, or a combination thereof

User interface 110 includes an input device, such as a touchscreen, keyboard or speech recognition subsystem, for enabling a user to communicate information and command selections to processor 115.

Processor 115 outputs, to user interface 110, a result of an execution of the methods described herein. Alternatively, processor 115 could direct the output to a remote device (not shown) via network 130 such that the appropriate PWM signal is sent to control the voltage to the PWM circuit (e.g., transistor circuit) 113 so as to modulate the voltage applied to ionic cleaner device 114.

While program module 125 is indicated as already loaded into memory 120, it may be configured on a storage medium 135 for subsequent loading into memory 120. Storage medium 135 can be any conventional storage medium that stores program module 125 thereon in tangible form. Examples of storage medium 135 include a floppy disk, a compact disk, a magnetic tape, a read only memory, an optical storage to media, universal serial bus (USB) flash drive, a digital versatile disc, or a zip drive. Alternatively, storage medium 135 can be a random access memory, or other type of electronic storage, located on a remote storage system and coupled to controller 105 via network 130.

Processor module 115 also has input/output ports, not shown, to transmit a control signal to a driver circuitry 113 located on the controller board, not shown, which in turn modulates the voltage sent to ionic cleaner device 114. Processor module 115 generates a low voltage (3.3V)-frequency signal (1 kHz) with varying On/Off times (keeping the total time duration the same), called the pulse width modulation (PWM).

FIG. 2 illustrates the logic diagram pertaining to the control of the power used to produce ozone in an ionic cleaner by PWM according to the present disclosure, wherein the ionic cleaner module is initialized or set-up 200, i.e. output port configuration and model table protocol is established. Thereafter, ionic device 114 is turned ‘on’ 202, the model number entered by the user interface is then compared 204 with the model table stored in memory 120, and, based on the model entered, the PWM % is set 206 by calculating the ‘on’ time and frequency for the driver transistor 113. Thereafter, the process is either complete 208 or returned to step 202 to turn on the ionic device.

FIG. 3 depicts a PWM driver circuit according to the present disclosure, wherein the driver circuitry, referred to herein as the PWM circuit, comprises a driving resistor(s) 302 and a metal oxide semiconductor field effect transistor 304 that receive a control signal from processor module 115 and converts it to a higher power level (e.g., 12 volts at 600 mA) and transmits it to ionic cleaner device 114.

FIG. 4 is an oscilloscope capture demonstrating that both the current and voltage vary as the PWM % varies, i.e. the voltage is varied in discrete steps from 100% to 75% of the 12 volt DC. This is accomplished by varying the ‘on’ time of this voltage signal while keeping the total duration of the signal constant (i.e. at 1 kHz which is 1 ms).

FIG. 6 depicts ozone generator or ionic cleaner 114 attached to ice making machine 600 via a bracket 602 that secures it to the bulkhead 604 and upper left rail 606. Air from ice making zone 612 is carried to and from ozone generator or ionic cleaner 114 via conduits or tubes 608, 610, respectively.

While we have shown and described several embodiments in accordance with our invention, it is to be clearly understood that the same may be susceptible to numerous changes apparent to one skilled in the art. Therefore, we do not wish to be limited to the details shown and described but intend to show all changes and modifications that come within the scope of the appended claims. 

1. A method for decontaminating air in an ice making machine, comprising: controlling the level of ozone outputted from an ozone generator by modulating the voltage using pulse width modulation; and contacting said air with said ozone.
 2. The method according to claim 1, wherein said level of ozone is about less than 0.1 ppm.
 3. The method according to claim 1, wherein said pulse width modulation controls the level of said ozone by controlling or manipulating the grams per hour of ozone introduced from said ozone generator into said ice making machine.
 4. The method according to claim 1, further comprising: comparing the model of said ice making machine to a look-up table; and determining the percentage of said pulse width modulation require to control said voltage by calculating the ‘on’ time and frequency for a pulse width modulation driver transistor based upon said model.
 5. The method according to claim 1, wherein said modulated voltage produced from said pulse width modulation is generated by an ozone control signal from a processor module and a pulse width modulation circuit.
 6. The method according to claim 5, wherein said pulse width modulation circuit comprises at least one driving resistor and a field effect transistor.
 7. The method according to claim 6, wherein said field effect transistor is a metal oxide semiconductor field effect transistor.
 8. An ice making machine comprising: an condenser; a compressor; an evaporator disposed within an ice making zone; and an ozone generator in communication with said ice making zone, wherein the level of ozone outputted from said ozone generator is controlled by modulating the voltage using pulse width modulation; and contacting air withdrawn from said ice making zone with said ozone and returning it to said ice making zone.
 9. The ice making machine according to claim 8, wherein said level of ozone is about less than 0.1 ppm.
 10. The ice making machine according to claim 8, wherein said pulse width modulation controls the level of said ozone by controlling or manipulating the grams per hour of ozone introduced from said ozone generator into said ice making zone.
 11. The ice making machine according to claim 8, further comprising: comparing the model of said ice making machine to a look-up table; and determining the percentage of said pulse width modulation require to control said voltage by calculating the ‘on’ time and frequency for a pulse width modulation driver transistor based upon said model.
 12. The ice making machine according to claim 8, wherein said modulated voltage produced from said pulse width modulation is generated by an ozone control signal from a processor module and a pulse width modulation circuit.
 13. The ice making machine according to claim 12, wherein said pulse width modulation circuit comprises at least one driving resistor and a field effect transistor.
 14. The ice making machine according to claim 13, wherein said field effect transistor is a metal oxide semiconductor field effect transistor. 